name: chemistry paper 1 required - a. hammond...

Chemistry Paper 1 RequiredPractical Past exam questions

Name: ________________________

Class: ________________________

Date: ________________________

Time: 231 minutes

Marks: 231 marks

Comments:

of 89The St Thomas the Apostle College

Colours are used to coat some chocolate sweets.

Some of these colours are given E-numbers.

Use the correct word from the box to complete the sentence.

additive element fuel

An E-number is used to identify a permitted food ........................................................

(1)

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(b) Chromatography was used to compare three of the colours used to coat the chocolatesweets.

What do these results tell you about these three colours?

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(3)

(Total 4 marks)


This question is about salts.

(a) Salt (sodium chloride) is added to many types of food.

Sodium chloride is produced by reacting sodium with chlorine.

sodium + chlorine sodium chloride

The diagram shows what happens to atoms of sodium and chlorine in this reaction.

The dots (•) and crosses (×) represent electrons.

Only the outer electrons are shown.

Describe, in terms of electrons, what happens when a sodium atom reacts with a chlorineatom to produce sodium chloride.

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(3)

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(b) Lack of iodine can affect the learning ability of children.

One idea is that salt (sodium chloride) should have iodine added.

(i) Iodine consists of simple molecules.

What is a property of substances that have simple molecules?

Tick ( ) one box.

Have no overall electriccharge

Have high boiling points

Have giant covalent structures

(1)

(ii) Which one of the following questions cannot be answered by science alone?

Tick ( ) one box.

How much sodium chloride is in food?

What harm does a lack of iodine do?

Should iodine be added to salt in food?

Give one reason why this question cannot be answered by science alone.

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(2)


(c) A student produced the salt ammonium nitrate by adding an acid to ammonia solution.

(i) Name the acid used.

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(1)

(ii) Use the correct answer from the box to complete the sentence.

an acid an alkali a salt

Ammonia solution (ammonium hydroxide) is ..................................... .

(1)

(iii) The student added a few drops of a solution which changed colour when the reactionwas complete.

Complete the sentence.

The solution added is an ............................................................. .

(1)

(d) Farmers buy solid ammonium nitrate in poly(ethene) sacks.

(i) How is solid ammonium nitrate made from a solution of ammonium nitrate?

Tick ( ) one box.

Crystallisation

Decomposition

Electrolysis

(1)


(ii) Why do farmers use ammonium nitrate on their fields?

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(1)

(iii) The properties of poly(ethene) depend on the reaction conditions when it is made.

State one reaction condition that can be changed when making poly(ethene).

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(1)

(Total 12 marks)

Hydrogen peroxide decomposes slowly to give water and oxygen.

The reaction is exothermic.

2H2O2 → 2H2O + O2

(a) In an exothermic reaction, energy is given out.

Draw a ring around the correct answer to complete the sentence.

goes down.

In an exothermic reaction, the temperature goes up.

stays the same.

(1)

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(b) The energy level diagram for this reaction is shown below.

The energy changes, A, B and C, are shown on the diagram.

Use the diagram to help you answer these questions.

(i) Which energy change, A, B or C, is the activation energy?

(1)

(ii) Which energy change, A, B or C, shows that this reaction is exothermic?

(1)


(iii) Hydrogen peroxide decomposes quickly when a small amount of manganese(IV)oxide is added.

Draw a ring around the correct answer to complete each sentence.

Hydrogen peroxide decomposes quickly because

a catalyst.

manganese(IV) oxide is an element.

a solid.

activation energy.

The manganese(IV) oxide has lowered the boiling point.

temperature.

(2)

(c) A student did an experiment to find the amount of energy produced when hydrogenperoxide solution is decomposed using manganese(IV) oxide.

The apparatus the student used is shown in the diagram.

The student first measured the temperature of the hydrogen peroxide. Then the studentadded the manganese(IV) oxide, stirred the mixture and recorded the highest temperature.

(i) Suggest why the student stirred the mixture before recording the highesttemperature.

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(1)


(ii) The biggest error in this experiment is heat loss.

Suggest how the student could change the apparatus so that less heat is lost.

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(1)

(Total 7 marks)

A student investigates the energy released when zinc powder reacts with copper sulfate solution.The student uses the apparatus shown in Figure 1.

The student:• measures 100 cm 3 copper sulfate solution into a beaker• measures the temperature of the copper sulfate solution• puts 1 g zinc powder into the beaker• stirs the mixture with a thermometer• measures the highest temperature.

The student’s results were:

Starting temperature = 21 °CHighest temperature = 32 °C

(a) (i) Calculate the change in temperature.

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Change in temperature = ........................................ °C

(1)

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(ii) Calculate the energy released in the reaction.

Use the equation

energy released

in J= volume of solution

in cm3

× 4.2 × temperature change in °C

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Energy released = ........................................ J

(2)

(b) The reaction of zinc with copper sulfate is exothermic.

How can you tell from the student’s results that the reaction is exothermic?

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(1)

(c) The energy diagram for the reaction is shown in Figure 2.

(i) How can you tell from the energy diagram that the reaction is exothermic?

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(1)


(ii) Which arrow shows the activation energy in Figure 2?

Tick ( ) one box.

A

B

C

(1)

(Total 6 marks)

(a) The diagram shows one way of making crystals of copper sulphate.

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(i) Why was the solution filtered?

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(1)

(ii) How could you make the crystals form faster from the copper sulphate solution?

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(1)

(iii) The chemical equation is shown for this reaction.

CuO(s) + H2SO4(aq) → CuSO4(aq) + H2O(l)

In the chemical equation what does (aq) mean?

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(1)


(b) Blue copper sulphate crystals go white when warmed. How could you use the white coppersulphate as a test for water?

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(2)

(Total 5 marks)

This question is about electrolysis.

(a) Metal spoons can be coated with silver.This is called electroplating.

Suggest one reason why spoons are electroplated.

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(1)

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(b) When sodium chloride solution is electrolysed the products are hydrogen and chlorine.

(i) What is made from chlorine?

Tick ( ) one box.

Bleach

Fertiliser

Soap

(1)


(ii) Sodium chloride solution contains two types of positive ions, hydrogen ions (H+) andsodium ions (Na+).

Why is hydrogen produced at the negative electrode and not sodium?

Tick ( ) one box.

Hydrogen is a gas.

Hydrogen is less reactive than sodium.

Hydrogen ions move faster than sodiumions.

(1)

(iii) Hydrogen and chlorine can be used to produce hydrogen chloride.

The diagrams in Figure 1 show how the outer electrons are arranged in an atom ofhydrogen and an atom of chlorine.

Complete Figure 2 to show how the outer electrons are arranged in a molecule ofhydrogen chloride (HCl).

(1)


(iv) What is the type of bond in a molecule of hydrogen chloride?

Tick ( ) one box.

Covalent

Ionic

Metallic

(1)

(v) Why is hydrogen chloride a gas at room temperature (20 °C)?

Tick ( ) two boxes.

Hydrogen chloride has a low boiling point.

Hydrogen chloride has a high melting point.

Hydrogen chloride is made of simple molecules.

Hydrogen chloride does not conduct electricity.

Hydrogen chloride has a giant structure.

(2)


(c) Aluminium is produced by electrolysis of a molten mixture of aluminium oxide and cryolite.This is shown in Figure 3.

(i) Name a gas produced at the positive electrode.

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(1)

(ii) Aluminium ions move to the negative electrode.

Explain why.

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(2)

(iii) At the negative electrode, the aluminium ions gain electrons to produce aluminium.

What is this type of reaction called?

Tick ( ) one box.

Combustion

Oxidation

Reduction

(1)


(iv) Aluminium has layers of atoms, as shown in Figure 4.

Complete the sentence.

Metals can be bent and shaped because the layers of atoms can ......

(1)

(d) Electrodes used in the production of aluminium are made from graphite.

(i) Which diagram, A, B or C, shows the structure of graphite?

The structure of graphite is shown in diagram

(1)

(ii) The temperature for the electrolysis is 950 °C.

Use the correct answer from the box to complete the sentence.

cross links a giant ionic lattice strong covalent bonds

The graphite does not melt at 950 °C because

graphite has ......................................................... .

(1)

(Total 14 marks)


Some pollutants cause acid rain.

A student tested 25.0 cm3 samples of three types of rainwater, P, Q and R.The student titrated the samples with sodium hydroxide solution (an alkali).

The student recorded the volume of sodium hydroxide solution needed to neutralise therainwater. The student’s results are shown in Table 1.

Table 1

Volume of sodium hydroxide needed to neutralise

the rainwater in cm3

Type ofrainwater

Titration 1 Titration 2 Titration 3 Titration 4Meanvalue

P 18.0 15.5 14.5 15.0 15.0

Q 13.0 10.0 11.0 10.5 10.5

R 23.0 19.5 18.5 19.0 19.0

(a) (i) The student calculated the mean value for rainwater R as 19.0 cm3.

Show how the student calculated the mean value for rainwater R.

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(2)

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(ii) Write down P, Q and R in order of their acidity.

Most acidic .............................

..............................

Least acidic .............................

(2)


(b) A second student repeated the experiment and recorded the results in Table 2.

Table 2

Volume of sodium hydroxide

needed to neutralise therainwater in cm3

Type ofrainwater

Titration 1 Titration 2

P 17 15

Q 11 9

R 20 18

Use Table 1 and Table 2 to suggest two improvements the second student could make toobtain more accurate results.

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(2)

(c) The results of the two students show that the experiment is reproducible.

Give the reason why.

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(1)

(Total 7 marks)


(a) A student used the apparatus in the figure below to do a titration.

(i) What is the name of the piece of apparatus labelled A?

Draw a ring around the correct answer.

burette measuring cylinder test tube

(1)

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(ii) What should the student add to the acid in the conical flask?

Draw a ring around the correct answer.

catalyst indicator water

(1)

(iii) What would the student see when the end point of the titration has been reached?

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(1)

(b) The student does the titration three times.

(i) State one variable that the student needs to keep the same to make it a fair test.

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(1)


(ii) The student’s results are shown in the table below.

TitrationVolume of sodium hydroxide solution

added in cm3

1 22.40

2 22.20

3 22.30

Calculate the mean volume of sodium hydroxide solution added.

........................................... cm3

(1)

(Total 5 marks)

Icing on cakes is tested to check that safe colours were used when they were made.

By Megan Chromik [CC-BY-SA-2.0], via Wikimedia Commons

Paper chromatography is one method of testing which colours are in cake icing.

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(a) The diagram shows an experiment a student did.

(i) Suggest why there is a lid on the container.

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(1)

(ii) The start line should be drawn in pencil not in ink.Suggest why.

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(1)


(b) The diagram shows the results of the paper chromatography experiment.

(i) How many different food colours were used in the colouring from the cake icing?

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(1)

(ii) Is the cake icing safe to eat?

Give a reason for your answer.

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(1)

(c) Gas chromatography linked to mass spectroscopy is an example of an instrumentalmethod. This method was used on a mixture of solvents.

(i) Give two advantages of gas chromatography compared with paper chromatography.

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(2)

(ii) What does gas chromatography do to the mixture of solvents?

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(1)


(iii) What information does mass spectroscopy give?

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(1)

(Total 8 marks)

The electrolysis of sodium chloride solution is an industrial process.

(a) Why do chloride ions move to the positive electrode?

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(1)

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(b) Sodium chloride solution contains two types of positive ions, sodium ions (Na+) and

hydrogen ions (H+).

Tick ( ) the reason why hydrogen is produced at the negative electrode and not sodium.

Reason Tick ( )

Hydrogen is a gas.

Hydrogen is less reactive than sodium.

Hydrogen is a non-metal.

Hydrogen ions travel faster than sodium ions.

(1)

(c) Solution X is alkaline.

Which ion makes solution X alkaline?

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(1)


(d) Electrolysis of sodium chloride solution produces hydrogen and chlorine.The hydrogen and chlorine can be used to make hydrogen chloride.

(i) The diagrams show how the outer electrons are arranged in atoms of hydrogen andchlorine.

Complete the diagram to show how the electrons are arranged in a molecule ofhydrogen chloride (HCl).

(1)

(ii) Name the type of bond between the hydrogen and the chlorine atoms in a moleculeof hydrogen chloride.

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(1)

(iii) Some hydrogen chloride was bubbled into water. This made a solution with a pH of 1.

Which ion gave the solution a pH of 1?

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(1)

(Total 6 marks)


A student investigated the electrolysis of sodium chloride solution.

Five sodium chloride solutions were made. Each solution had a different concentration.

To make each solution the student:

• weighed the amount of sodium chloride needed

• dissolved it in water

• added more water until the total volume was one cubic decimetre (1 dm 3).

The solutions were placed one at a time in the apparatus shown below.

The student measured the volume of hydrogen gas produced in ten minutes.

The results are shown on the graph below.

(a) Sodium chloride does not conduct electricity when it is solid.

Explain, in terms of ions, why sodium chloride solution conducts electricity.

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(1)

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(b) Chlorine is produced at the positive electrode.

Why are chloride ions attracted to the positive electrode?

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(1)


(c) The solution left at the end of each experiment contains sodium hydroxide.

Draw a ring around one number which could be the pH of this solution.

2 5 7 13

(1)

(d) The results for the experiment above are shown on the graph.

(i) Draw a line of best fit on the graph.

(1)


(ii) The result for one concentration is anomalous.Which result is anomalous?

The result at concentration ........................ grams per dm3

(1)

(iii) Suggest two possible causes of this anomalous result.

1 ............................................................................................................

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2 ............................................................................................................

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(2)

(iv) Suggest how the student could check the reliability of the results.

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(1)

(iv) How did an increase in the concentration of the sodium chloride solution affect thevolume of hydrogen gas produced in ten minutes?

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(1)

(Total 9 marks)


Methanol (CH3OH) can be made by reacting methane (CH4) and oxygen (O2).The reaction is exothermic.

The equation for the reaction is:

(a) The energy level diagram for this reaction is given below.

(i) How does the diagram show that this reaction is exothermic?

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(1)

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(ii) A platinum catalyst can be used to increase the rate of this reaction.

What effect does adding a catalyst have on the energy level diagram?

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(1)


(b) The equation can also be written showing the structural formulae of the reactants and theproduct.

(i) Use the bond energies given in the table to help you to calculate the energy changefor this reaction.

Bond Bond energy in kJ

435

497

336

464

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Energy change = ........................................ kJ

(3)

(iii) In terms of the bond energies, why is this an exothermic reaction?

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(1)

(Total 6 marks)


The label shows the ingredients in a drink called Cola.

Cola

Ingredients:

Carbonated waterSugarColouringPhosphoric acidFlavouringCaffeine

(a) (i) The pH of carbonated water is 4.5.

The pH of Cola is 2.9.

Name the ingredient on the label that lowers the pH of Cola to 2.9.

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(1)

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(ii) Which ion causes the pH to be 2.9?

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(1)


(b) A student investigated the food colouring in Cola and in a fruit drink using paperchromatography.

The chromatogram in the figure below shows the student’s results.

Cola Fruit drink

(i) Complete the sentence.

The start line should be drawn with a ruler and ...................................... .


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(2)

(ii) Suggest three conclusions you can make from the student’s results.

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(3)

(c) Caffeine can be separated from the other compounds in the drink by gas chromatography.

Why do different compounds separate in a gas chromatography column?

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(1)


(d) Caffeine is a stimulant.

Large amounts of caffeine can be harmful.

(i) Only one of the questions in the table can be answered by science alone.

Tick ( ) one question.

Question Tick ( )

Should caffeine be an ingredient in drinks?

Is there caffeine in a certain brand ofdrink?

How much caffeine should people drink?

(1)

(ii) Give two reasons why the other questions cannot be answered by science alone.

Reason 1 ..............................................................................................

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Reason 2 ..............................................................................................

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(2)

(Total 11 marks)


Read the information about energy changes and then answer the questions.

A student did an experiment to find the energy change when hydrochloric acid reacts withsodium hydroxide.

The equation which represents the reaction is:

HCl + NaOH → NaCl + H2O

The student used the apparatus shown in the diagram.

The student placed 50 cm3 of hydrochloric acid in a glass beaker and measured the initialtemperature.

The student then quickly added 50 cm3 of sodium hydroxide solution and stirred the mixture withthe thermometer. The highest temperature was recorded.

The student repeated the experiment, and calculated the temperature change each time.

Experiment

1Experiment

2Experiment

3Experiment

4

Initial temperaturein °C

19.0 22.0 19.2 19.0

Highest temperaturein °C

26.2 29.0 26.0 23.5

Temperaturechange in °C

7.2 7.0 6.8 4.5

(a) The biggest error in this experiment is heat loss.

Suggest how the apparatus could be modified to reduce heat loss.

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(1)

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(b) Suggest why it is important to mix the chemicals thoroughly.

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(1)

(c) Which one of these experiments was probably done on a different day to the others?


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(1)

(d) Suggest why experiment 4 should not be used to calculate the average temperaturechange.

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(1)

(e) Calculate the average temperature change from the first three experiments.

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Answer = .................................................. °C

(1)

(f) Use the following equation to calculate the energy change for this reaction.

Energy change in joules = 100 × 4.2 × average temperature change

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Answer = .................................................. J

(1)


(g) Which one of these energy level diagrams represents the energy change for thisreaction?


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(1)

(Total 7 marks)

In this question you will be assessed on using good English, organising information clearly andusing specialist terms where appropriate.

A student used the equipment shown to do a titration.

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Describe how the student should use this equipment to find the volume of sodium hydroxidesolution that reacts with a known volume of acid.Include any measurements the student should make.

Do not describe how to do any calculations.

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(Total 6 marks)


The diagram shows apparatus used by a student to investigate electrolysis.

The student was given a solution by the teacher. The solution contained a mixture of ioniccompounds.

(a) Name the particles which carry the electric current through:

(i) the metal wires .....................................................................................

(1)

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(ii) the solution. ..........................................................................................

(1)

(b) The table shows the ions in the solution.

Positive ions in the solution Negative ions in the solution

Zinc ion (Zn2+) Chloride ion (Cl–)

Iron(III) ion (Fe3+) Hydroxide ion (OH–)

Hydrogen ion (H+) Nitrate ion (NO3–)

Copper(II) ion (Cu2+) Sulfate ion (SO42–)

The reactivity series on the Data Sheet may help you to answer this question.

(i) Which element is most likely to be formed at the negative electrode?

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(1)


(ii) Explain, as fully as you can, why you have chosen this element.

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(2)

(c) The electrolysis of sodium chloride solution is an industrial process.

(i) The reaction at one of the electrodes can be represented by the equation shownbelow.

2Cl– → Cl2 + 2e–

The chloride ions (Cl–) are oxidised.

Explain why.

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(1)

(ii) The reaction at the other electrode can be represented by an equation.

Complete and balance the equation for the reaction at the other electrode.

H+ → H2

(1)

(Total 7 marks)


A student investigates the energy released when hydrochloric acid completely neutralisessodium hydroxide solution.The student uses the apparatus shown in Figure 1.

The student:• measures 25 cm 3 sodium hydroxide solution into a polystyrene cup• fills a burette with hydrochloric acid• measures the temperature of the sodium hydroxide solution• adds 5 cm 3 hydrochloric acid to the sodium hydroxide solution in the polystyrene cup• stirs the mixture and measures the highest temperature of the mixture• continues to add 5 cm 3 portions of hydrochloric acid, stirring and measuring the highest

temperature of the mixture after each addition.

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(a) The student has plotted a graph of the results.

The graph line has been incorrectly drawn by including an anomalous result.

The graph is shown in Figure 2.

(i) Suggest a cause for the anomalous result when 20 cm3 of hydrochloric acid is added.

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(1)

(ii) Suggest the true value of the temperature of the anomalous point.

Temperature = .............................. °C

(1)

(iii) What was the total volume of the mixture when the maximum temperature wasreached?

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Total volume of the mixture = .............................. cm3

(1)

(iv) Calculate the overall temperature increase in this experiment.

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Overall temperature increase = .............................. °C

(1)


(v) Use your answers to (iii) and (iv) and the equation to calculate the energy released inthe reaction. Give the unit.

Assume the volume in cm3 is equivalent to the mass of solution in grams.

Equation: Q = mcΔT

where:Q = energy releasedm = mass of solution (g)c = 4.2 (J per g per °C)ΔT = change in temperature (°C)

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Energy released = .............................. Unit = ....................

(2)

(b) The student did the experiment again, starting with 50 cm3 of sodium hydroxide solutioninstead of 25 cm3.

Explain why this would make no difference to the overall temperature increase.

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(2)

(Total 8 marks)

A student carried out a titration to find the concentration of a solution of sulphuric acid. 25.0 cm3

of the sulphuric acid solution was neutralised exactly by 34.0 cm3 of a potassium hydroxide

solution of concentration 2.0 mol/dm3. The equation for the reaction is:

2KOH(aq) + H2SO4(aq) → K2SO4(aq) + 2H2O(l)

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(a) Describe the experimental procedure for the titration carried out by the student.

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(4)

(b) Calculate the number of moles of potassium hydroxide used.

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Number of moles = .......................................

(2)

(c) Calculate the concentration of the sulphuric acid in mol/dm3.

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Concentration = .................................. mol/dm3

(3)

(Total 9 marks)


Insoluble salts can be made by mixing solutions of two soluble salts.

(a) A student mixed sodium carbonate solution and copper sulfate solution.

This produced a precipitate of copper carbonate and a solution of sodium sulfate.

(i) Write the correct state symbols from the box in the spaces in the chemical equation.

aq g l s

Na2CO3(aq) + CuSO4(aq) CuCO3 (..........) + Na2SO4 (..........)

(2)

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(ii) What process could the student use to separate the precipitate of copper carbonatefrom the mixture?

Tick ( ) one box.

Chromatography

Distillation

Filtration

(1)

(iii) The student washed the copper carbonate he obtained with water.

Name one substance removed from the copper carbonate by washing it with water.

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(1)


(b) A student mixed some salt solutions.

His observations are shown the table.

Mixture Salt solution 1 Salt solution 2 Observations

A Sodium carbonate Cobalt sulfatePink precipitate

Colourless solution

B Copper sulfate Lead nitrateWhite precipitate

Blue solution

C Sodium sulfate Manganese nitrateNo precipitate

Very pale pink solution

• All sodium salts are soluble.• All nitrate salts are soluble.

(i) Name the insoluble salt made in mixture B.

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(1)

(ii) Name one soluble salt made by the student.

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(1)

(iii) What colour is cobalt carbonate?

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(1)


(c) Barium sulfate is an insoluble salt.

Barium sulfate can be made by adding barium hydroxide solution to dilute sulfuric acid.

The balanced chemical equation for the reaction is:

H2SO4(aq) + Ba(OH)2(aq) BaSO4(s) + 2 H2O(l)

A student investigated how the electrical conductivity of dilute sulfuric acid changed asbarium hydroxide solution was added.

This is the method she used.

Step 1 Place 25.0 cm3 of dilute sulfuric acid in a conical flask.Step 2 Add 5.0 cm3 of barium hydroxide solution.Step 3 Stir the mixture.Step 4 Use a conductivity meter to measure the electrical conductivity of the mixture.Step 5 Repeat Step 2, Step 3 and Step 4 until 50 cm3 of barium hydroxide

solution have been added.

The student’s results are shown on the graph.

(i) The ringed point on the graph is anomalous.

What could have happened to cause the anomalous point?

Tick ( ) one box.


No more barium hydroxide solution was added.

Too much barium hydroxide solution was added.

Too much dilute sulfuric acid was used.

(1)

(ii) Use the graph to estimate the relative electrical conductivity of the dilute sulfuric acidbefore any barium hydroxide solution was added.

Show your working on the graph.

Relative electrical conductivity = ........................................

(2)

(iii) Explain why dilute sulfuric acid conducts electricity.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)


(d) The graph has been reprinted here to help you to answer the questions.

(i) What was the volume of barium hydroxide solution added when the relative electricalconductivity of the mixture was zero?

Volume of barium hydroxide solution = .................... cm3

(1)

(ii) Suggest why the relative electrical conductivity became zero.

...............................................................................................................

...............................................................................................................

...............................................................................................................

(1)


(e) The student did another experiment using the same solutions as she used before.

She used the same volume (25.0 cm3) of dilute sulfuric acid in the conical flask.

She then added an unknown volume of barium hydroxide solution.

She found that the relative electrical conductivity of the mixture was 260.

This is the student’s conclusion:

13 cm3 of barium hydroxide solution must have been added.

(i) Why may the student’s conclusion not be correct?

...............................................................................................................

...............................................................................................................

(1)

(ii) The student said that she could check whether she was correct by adding somethingto the mixture.

What could she add to the mixture? How would this tell her whether she was correct?

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

(3)

(Total 18 marks)

(a) Copper sulfate crystals can be made from copper oxide and dilute sulfuric acid.

In this question you will be assessed on using good English, organising informationclearly and using specialist terms where appropriate.

Give a method for making copper sulfate crystals from copper oxide and dilutesulfuric acid.

20


You should include:

• the names of the pieces of apparatus used

• the purpose of each step

• appropriate safety precautions.

........................................................................................................................

........................................................................................................................

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........................................................................................................................

........................................................................................................................

(6)

(b) If crystals of hydrated copper(II) sulfate are dried by heating them strongly, theydecompose to give a white solid.

The equation for this decomposition is:

CuSO4. 5H2O CuSO4 + 5H2O

(i) Give the name of the white solid formed.

...............................................................................................................

(1)


(ii) Dilute sulfuric acid was added to the white solid.What colour would the white solid turn?Explain your answer.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)

(Total 9 marks)


Chromatography can be used to separate components of a mixture.

(a) A student used paper chromatography to analyse a black food colouring.

The student placed spots of known food colours, A, B, C, D and E, and the black foodcolouring on a sheet of chromatography paper.

The student set up the apparatus as shown in Diagram 1.

Diagram 1

The student made two errors in setting up the apparatus.Identify the two errors and describe the problem each error would cause.

.........................................................................................................................

.........................................................................................................................

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.........................................................................................................................

.........................................................................................................................

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.........................................................................................................................

(4)

21


(b) A different student set up the apparatus without making any errors.

The chromatogram in Diagram 2 shows the student’s results.

Diagram 2

(i) What do the results tell you about the composition of the black food colouring?

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)

(ii) Use Diagram 2 to complete Table 1.

Table 1

Distance in mm

Distance from start line to solvent front .............................

Distance moved by food colour C .............................

(2)

(iii) Use your answers in part (b) (ii) to calculate the Rf value for food colour C.

...............................................................................................................

...............................................................................................................

Rf value = ........................................

(1)


(c) Table 2 gives the results of chromatography experiments that were carried out on someknown food colours, using the same solvent as the students.

Table 2

Name of food

colour

Distance from startline to solvent front

in mm

Distance moved byfood colour in mm

Rf value

Ponceau 4R 62 59 0.95

Carmoisine 74 45 0.61

Fast red 67 27 0.40

Erythrosine 58 17 0.29

Which of the food colours in Table 2 could be food colour C from the chromatogram?

Give the reason for your answer.

.........................................................................................................................

.........................................................................................................................

.........................................................................................................................

(2)

(d) Two types of chromatography are gas chromatography and paper chromatography.

Give one advantage of gas chromatography compared with paper chromatography.

.........................................................................................................................

.........................................................................................................................

(1)

(Total 12 marks)

Calcium chloride (CaCl2) is a soluble salt.

Calcium chloride can be made by reacting dilute hydrochloric acid with either solid calcium oxideor solid calcium carbonate.

(a) Name the type of reaction that takes place when dilute hydrochloric acid reacts withcalcium oxide.

........................................................................................................................

(1)

22


(b) Write a balanced symbol equation for the reaction of dilute hydrochloric acid with calciumoxide.

........................................................................................................................

(2)

(c) A student added solid calcium oxide to dilute hydrochloric acid in a beaker.

The student added solid calcium carbonate to dilute hydrochloric acid in another beaker.

Describe one difference between the two reactions that the student would see.

........................................................................................................................

........................................................................................................................

(1)

(d) Describe how crystals of calcium chloride can be made from calcium carbonate and dilutehydrochloric acid.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

(4)

(e) A student dissolved some crystals of a salt in water.

The student added sodium hydroxide solution to the salt solution.

The student added sodium hydroxide solution until it was in excess.

(i) Describe what the student would see if the salt contained calcium ions.

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)


(ii) Why does the result you have described in part (e)(i) not prove that the salt containscalcium ions?

...............................................................................................................

...............................................................................................................

(1)

(iii) Describe an additional test the student could do that would prove the salt containscalcium ions.

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)

(Total 13 marks)

A student investigated the rate of reaction of magnesium and hydrochloric acid.

Mg(s) + 2HCl(aq) MgCl2(aq) + H2(g)

The student studied the effect of changing the concentration of the hydrochloric acid.

She measured the time for the magnesium to stop reacting.

Concentration ofhydrochloric acid

in moles per dm3

0.5 1.0 1.5 2.0

(a) The student changed the concentration of the hydrochloric acid.

Give two variables that the student should control.

1 ....................................................................................................................

2 ....................................................................................................................

(2)

23


(b) (i) The rate of reaction increased as the concentration of hydrochloric acid increased.

Explain why.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)

(ii) Explain why increasing the temperature would increase the rate of reaction.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

(3)


(c) (i) The student had a solution of sodium hydroxide with a concentration of 0.100 moles

per dm3.

She wanted to check the concentration of a solution of hydrochloric acid.

She used a pipette to transfer 5.00 cm3 of the hydrochloric acid into a conical flask.

She filled a burette with the 0.100 moles per dm3 sodium hydroxide solution.

Describe how she should use titration to obtain accurate results.

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(4)


(ii) Sodium hydroxide neutralises hydrochloric acid as shown in the equation:

NaOH(aq) + HCl(aq) NaCl(aq) + H2O(l)

The student found that 27.20 cm3 of 0.100 moles per dm3 sodium hydroxide

neutralised 5.00 cm3 of hydrochloric acid.

Calculate the concentration of the hydrochloric acid in moles per dm3.

Give your answer to three significant figures.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Concentration of hydrochloric acid = .............................. moles per dm3

(3)

(Total 14 marks)


Dilute nitric acid reacts with potassium hydroxide solution.

The equation for the reaction is:

HNO3 + KOH KNO3 + H2O

A student investigated the temperature change in this reaction.

This is the method the student used.

Step 1 Put 25 cm3 of dilute nitric acid in a polystyrene cup.Step 2 Use a thermometer to measure the temperature of the dilute nitric acid.Step 3 Use a burette to add 4 cm3 of potassium hydroxide solution to the dilute nitric acid

and stir the mixture.Step 4 Use a thermometer to measure the highest temperature of the mixture.Step 5 Repeat steps 3 and 4 until 40 cm3 of potassium hydroxide solution have been added.

The dilute nitric acid and the potassium hydroxide solution were both at room temperature.

(a) Figure 1 shows part of the thermometer after some potassium hydroxide solution had beenadded to the dilute nitric acid.

What is the temperature shown on the thermometer?

The temperature shown is .................... °C

(1)

24

(b) Errors are possible in this experiment.

(i) Suggest two causes of random error in the experiment.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)


(ii) Another student used a glass beaker instead of a polystyrene cup.

This caused a systematic error.

Why does using a glass beaker instead of a polystyrene cup cause a systematicerror?

...............................................................................................................

...............................................................................................................

...............................................................................................................

(1)

(c) The results of the student using the polystyrene cup are shown in Figure 2.

(i) How do the results in Figure 2 show that the reaction between dilute nitric acid andpotassium hydroxide solution is exothermic?

...............................................................................................................

...............................................................................................................

(1)

(ii) Explain why the temperature readings decrease between 28 cm3 and 40 cm3 ofpotassium hydroxide solution added.

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)


(iii) It is difficult to use the data in Figure 2 to find the exact volume of potassiumhydroxide solution that would give the maximum temperature.

Suggest further experimental work that the student should do to make it easier to findthe exact volume of potassium hydroxide solution that would give the maximumtemperature

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)

(d) The student did further experimental work and found that 31.0 cm3 of potassium hydroxidesolution neutralised 25.0 cm3 of dilute nitric acid.

The concentration of the dilute nitric acid was 2.0 moles per dm3.

HNO3 + KOH KNO3 + H2O

Calculate the concentration of the potassium hydroxide solution in moles per dm3.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Concentration = ............................ moles per dm3

(3)


(e) The student repeated the original experiment using 25 cm3 of dilute nitric acid in apolystyrene cup and potassium hydroxide solution that was twice the original concentration.

She found that:

• a smaller volume of potassium hydroxide solution was required to reach themaximum temperature

• the maximum temperature recorded was higher.

Explain why the maximum temperature recorded was higher.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

(2)

(Total 14 marks)

A student analysed a sample of water from a disused mine to find out which metal ions were inthe water.

He used paper chromatography of the sample of water from the mine and of solutionscontaining known metal ions.

He set the apparatus up as shown in the diagram.

25


(a) Give one error the student made in the way he set up his apparatus.Explain the problem this error would have caused.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

(2)

(b) Another student repeated the experiment, but without making any errors.

After the water had soaked up the chromatography paper he sprayed it with a dilutesolution of sodium hydroxide. Coloured spots appeared on the paper.

The results he obtained are shown in the diagram.

(i) Identify two of the metal ions in the sample of water from the mine.

...............................................................................................................

(1)

(ii) State the colour of the spot formed from the iron(III) ions.

...............................................................................................................

(1)

(iii) Give the formula of the iron(III) compound responsible for the colour you statedin (b)(ii).

(1)


(c) Spots obtained by chromatography can be compared by their Rf values.

(i) Use the diagram of the results to help you to complete the table.

Include the units.

distance moved by spot X frombase line

..............

distance moved by solvent frombase line

..............

(2)

(ii) Use the values you recorded in the table to calculate the Rf value for spot X.

...............................................................................................................

...............................................................................................................

Rf value = .......................................................................

(1)

(d) Paper chromatography of a mixture using water as the solvent gave a spot with an Rf

value of 0.54.

The data in the table below was used to identify the substance that caused the spot.

Substance

Rf value when the solvent is:

Water Ethanol Propanone

A 0.72 0.54 0.00

B 0.53 0.62 0.84

C 0.04 0.16 0.54

D 0.55 0.45 0.31

(i) Use the data in the table to suggest two possible identities for the substancethat caused the spot with an Rf of 0.54.

.......................................................................................

.......................................................................................

(1)


(ii) Describe a further chromatography experiment that should be carried out toconfirm which one of the substances you have identified in (d)(i) actuallycaused the spot.Explain why you chose this experiment.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)

(Total 11 marks)


Mark schemes

(a) additive11

(b) colour 3 is a mixture of colours 1 and 2

any two from:

accept E-number or additive instead of colour

ignore comments about height / level1

• colour 1 is made up of only one colour / dye

• colour 2 is made up of only one colour / dye

• colour 3 is made up of two colours / dyesormore colours (than colours 1 and 2)

2

[4]

(a) sodium loses (electron)

sharing / covalent / metallic = max 21

chlorine gains (electron)1

1 or an (electron)1

2

(b) (i) Have no overall electric charge1

(ii) Should iodine be added to salt?1

reasonany one from:• cannot be done by experiment

accept difficult to get / not enough evidence• based on opinion / view

allow must be done by survey• ethical or economic issue.

1


(c) (i) nitric (acid)1

(ii) an alkali1

(iii) indicator

accept any named acid base indicator1

(d) (i) Crystallisation1

(ii) fertiliser

allow to help crops grow1

(iii) any one from:• pressure

allow concentration• temperature

ignore heat• catalyst.

1

[12]

(a) goes up1

3

(b) (i) B1

(ii) A1

(iii) a catalyst1

activation energy1

(c) (i) eg (ensures) complete reaction

allow spread heat / energy

or even heating

allow mixes properly or mix them together or to get correcttemperature

ignore dissolves1


(ii) lid (on beaker)

accept cover beaker

or

insulate (beaker) / use a plastic cup1

[7]

(a) (i) 111

(ii) 4620 (J)

correct answer gains 2 marks with or without working

allow 4.62kJ for 2 marks

if answer is incorrect:

100 × 4.2 × 11 gains 1 mark

or

100 × 4.2 × (their temp. rise) gains 1 mark

or

100 × 4.2 × (their temp. rise) correctly calculated gains 2 marks2

4

(b) the temperature increases

allow gets hotter

allow heat / energy is given off1

(c) (i) (energy of) products lower than (energy of) reactants

allow converse

allow arrow C points downwards1

(ii) A1

[6]

(a) (i) to remove or separate copper oxide

accept to remove or separate

unreacted or excess base

accept to remove or separate insoluble solids1

5


(ii) heat (the solution)

accept heat the water

accept evaporate the water

rapid cooling/cool to lower temperature

accept boil the water or solution

not increase surface area, put in

draught

not increase the temperature1

(iii) aqueous

accept in water

accept solution

not soluble in water1

(b) add water/liquid/solution1

colour changes to blue1

[5]

(a) any one from:• protection / improve lifespan• improve appearance.

1

6

(b) (i) Bleach1

(ii) Hydrogen is less reactive than sodium1

(iii) 1 bonding pair of electrons 6 unbonded electrons on Cl

accept dot, cross or e or − or any combination1

(iv) Covalent1

(v) Hydrogen chloride has a low boiling point.1

Hydrogen chloride is made of simple molecules.1


(c) (i) oxygen

accept carbon dioxide1

(ii) aluminium ions are positive1

so are attracted (to the negative electrode)

allow opposites attract1

(iii) Reduction1

(iv) slide

allow move1

(d) (i) C1

(ii) strong covalent bonds1

[14]

(a) (i) (19.5 + 18.5 + 19.0) / 3

allow (23.0 + 19.5 + 18.5 + 19.0) / 4 for 1 mark2

(ii) R P Q

allow Q P R for 1 mark2

7

(b) any two from:• repeat more times• calculate a mean• measure to one decimal place.

2

(c) both students get similar results / similar pattern1

[7]


(a) (i) burette1

(ii) indicator1

(iii) colour change1

(b) (i) any one from:• volume of (hydrochloric) acid

allow amount of (hydrochloric) acid• concentration of (hydrochloric) acid• concentration of (sodium) hydroxide

allow concentration of alkali1

(ii) 22.3(0)1

[5]

8

(a) (i) prevent evaporation of solvent

allow prevent loss of solvent

allow to support the (chromatography) paper1

9

(ii) ink dissolves in the solvent

allow ink ‘runs’ / spreads or pencil does not ‘run’ / spread

allow ink would affect the result / mixes with colours

or

carbon / graphite does not dissolve in the solvent

accept pencil for carbon / graphite1

(b) (i) 41

(ii) no mark for ‘no / don’t know’ ,

ignore numbers

any one from:

• because not all colours match

• not all colours are safe

• some colours could be unsafe

• some colours travelled higher (than safe colours)1


(c) (i) any two from:

ignore reliable / precise

• rapid / quick

• accurate

• sensitive or detects very small quantities

accept small sample2

(ii) separates1

(iii) identifies solvents / compounds / substances

accept (relative) molecular mass

accept formula mass

accept Mr

accept relative mass

accept molecular ion peak1

[8]

(a) any one from:

• they are negative / anions

allow Cl–

ignore atoms / chlorine

do not accept chloride ions are negative electrodes

• they are attracted

• they are oppositely charged1

10

(b) hydrogen is less reactive than sodium1

(c) hydroxide (ions) / OH–

ignore OH

do not accept NaOH / sodium hydroxide1


(d) (i)

allow any combination of dots or crosses

ignore chemical symbols1

(ii) covalent

allow close spelling errors

apply list principle1

(iii) hydrogen (ion) / H+

ignore (aq) / H

do not accept hydrochloric acid / HCl

apply list principle1

[6]

(a) the ions can move / travel / flow /are free

accept particles / they for ions

allow delocalised ions

or

ignore delocalised / free electrons

ignore references to collisions

accept converse with reference to solid

the ions carry the charge / current

ignore ions carry electricity1

11

(b) any one from:

• because they are negative / anion

allow Cl–

ignore chlorine

• opposite charges / attract1

(c) 131


(d) (i) reasonable attempt at straight line which misses the anomalous point

must touch all five crosses

do not allow multiple lines1

(ii) 40

ignore 2.21

(iii) any two sensible errors from:

ignore systematic / human / apparatus / zero /experimental /random / measurement / reading errors unless qualified

• gas escapes

• weighing error

allow NaCl not measured correctly

• error in measuring (volume / amount) of hydrogen

• error in measuring (volume / amount) of water

allow error in measuring volume / scale for 1 mark if neitherhydrogen or water mentioned

• incorrect concentration

allow NaCl not fully dissolved or spilled or impure

• timing error

• change in voltage / current

allow faulty power supply

• change in temperature

• recording / plotting error2

(iv) any one from:

ignore ‘do more tests’

• repeat the experiment

• results compared with results from /other students / other groups / otherlaboratories / internet / literature.

• results compared with another method1

(v) increases owtte

allow directly proportional or positive correlation

allow rate / it is faster / quicker1

[9]


(a) (i) energy / heat of products less than energy of reactants

allow converse

allow products are lower than reactants

allow more energy / heat given out than taken in

allow methanol is lower

allow energy / heat is given out / lost

allow ΔH is negative1

12

(ii) lowers / less activation energy

allow lowers energy needed for reactionor it lowers the peak/ maximum

do not allow just ‘lowers the energy’1

(b) (i) (8 × 435) + 497 = 3977

accept: bonds broken: (2 × 435) + 497 = 13671

(6 × 435) + (2 × 336) + (2 × 464) = 4210

bonds made: (2 × 336) + (2 × 464) = 16001

3977 – 4210 = (–) 233

energy change:

1367 – 1600 = (–) 233

ignore sign

allow ecf

correct answer (233) = 3 marks with or without working1

(ii) energy released forming (new) bonds is greater than energy needed to break(existing) bonds

allow converse

do not accept energy needed to form (new) bonds greater thanenergy needed to break (existing) bonds

1

[6]


(a) (i) (phosphoric) acid

allow phosphoric1

(ii) H+ / hydrogen (ion)

if ion symbol given, charge must be correct1

(b) (i) pencil1

so it will not run / smudge / dissolve

ignore pencil will not interfere with / affect the results

or

because ink would run / smudge / dissolve

ignore ink will interfere with / affect the results1

(ii) any three from:

reference to spots / dots = max 2

allow colouring for colour• 3 colours in Cola

allow more colours in cola or fewer colours in fruit drink• 2 colours in Fruit drink• one of the colours is the same• two of the colours in Cola are different• one of the colours in Fruit drink is different

allow some of the colours in the drinks are different• one of the colours in Cola is the most soluble

accept one of the colours in Cola has the highest Rf value3

(c) different substances travel at different speeds or have different retention times

accept different attraction to solid

ignore properties of compounds1

(d) (i) Is there caffeine in a certain brand of drink?1

(ii) any two from:

• cannot be done by experiment• based on opinion / lifestyle choice• ethical, social or economic issue

accept caffeine has different effects on different people2

[11]

13


(a) eg plastic (beaker) / insulation / lid / cover or any mention of enclosed

any sensible modification to reduce heat loss

ignore prevent draughts

ignore references to gas loss

ignore bomb calorimeter1

14

(b) all the substances react or all (the substances) react fully / completely or heatevolved quickly or distribute heat

‘so they react’ is insufficient for the mark

accept increase chances of (successful) collisions / collision rateincrease

do not accept rate of reaction increase / make reaction faster1

(c) experiment 2 anddifferent / higher / initial / starting temperature

accept experiment 2 and the room is hotter / at higher temperature

do not accept temperature change / results higher1

(d) temperature change does not fit pattern

accept anomalous / odd or it is the lowest or it is lower than theothers or it is different to the others

‘results are different’ is insufficient1

(e) 7 / 7.01

(f) (100 × 4.2 × 7) = 2940

ecf from (e)1

(g) diagram A andreaction exothermic / heat evolved / Δ H is negative / temperature rises

accept energy is lost (to the surroundings)

accept energy of products lower than reactants

allow arrow goes downwards1

[7]


Marks awarded for this answer will be determined by the Quality of Written Communication(QWC) as well as the standard of the scientific response. Examiners should also refer to theinformation in the Marking guidance.

0 marksNo relevant content.

Level 1 (1-2 marks)There is a simple description of using some of the equipment.

Level 2 (3-4 marks)There is a description of an experimental method involving a measurement, or including additionof alkali to acid (or vice versa).

Level 3 (5-6 marks)There is a description of a titration that would allow a successful result to be obtained.

15

Examples of chemistry points made in the response could include:

• acid in (conical) flask

• volume of acid measured using pipette

• indicator in (conical) flask

• sodium hydroxide in burette

• white tile under flask

• slow addition

• swirling

• colour change

• volume of sodium hydroxide added

Extra information

• allow acid in the burette to be added to sodium hydroxide in the (conical) flask

• allow any specified indicator

colour change need not be specified

[6]

(a) (i) electron(s)

allow free / delocalised / negative electrons

do not accept additional particles1

16


(ii) ion(s)

allow named ions from table

ignore positive or negative

do not accept additional particles1

(b) (i) copper

accept Cu

do not accept Cu2+

1

(ii) it is / they are positive (ions)

accept formula of positive ion1

and it is the least reactive1

(c) (i) loss of electron(s)

ignore numbers1

(ii) 2H+ + 2e– → H2

accept correct multiples / fractions

accept e / e–

allow 2H+ → H2 – 2e–

1

[7]

(a) (i) any one from:

• incorrect measurement of temperature or volume• incorrect recording of temperature• failure to stir• heat loss

ignore faulty equipment1

17

(ii) 32 - 331

(iii) 551

(iv) 201

(v) 4620

allow 4.62 kJ for 2 marks1


J / joules

allow kJ if evidence of dividing by 1000

mark independently, but if a numerical answer has been divided by1000 must be kJ.

allow ecf from their answers to (iii) and (iv)1

(b) twice as much energy released1

but twice as much water to heat

allow more energy released but more water to heat for 2 marks

if no other mark awarded, allow twice the amount of hydrochloricacid used for 1 mark

1

[8]

(a) any four from:

• sulphuric acid measure by pipette

or diagram

• potassium hydroxide in burette

or diagram

• if solutions reversed, award

• note initial reading

• use of indicator

• note final reading or amount used4

18

(b) 1

= 0.0681

(c) ½ or 0.5 moles H2SO4 react with 1 mole KOH1

moles H2SO4 in 25.0 cm3 = 0.068 × 0.51

moles H2SO4 in 1 dm3 = = 1.36 mol/dm3

1

[9]


(a) (i) s

this order only1

aq1

(ii) Filtration1

(iii) sodium carbonate or copper sulfate or sodium sulfate

accept correct formulae1

19

(b) (i) lead sulfate

accept correct formula1

(ii) sodium sulfate or copper nitrate or sodium nitrate or manganese sulfate

accept correct formula1

(iii) (very pale) pink1

(c) (i) No more barium hydroxide solution was added1

(ii) correct extrapolation shown on graph1

640

correct answer with no extrapolation shown gains 1 mark1

(iii) contains ions1

which are able to move

second mark dependent on having ions1

(d) (i) 21.5 (cm3)

accept 21 to 221

(ii) no dissolved (ionic) substance or ions cannot move or liquid is water or no ionsin solution

1


(e) (i) could have added 39 cm3 or another volume gives the same conductivity1

(ii) add (more) barium hydroxide1

a small volume

if specified the volume must be less than 26 cm3

1

if she is correct this will cause the conductivity to droporallow add a named indicatorcorrect acid colour for this indicatorsome acid remains in solution

1

[18]

(a) Marks awarded for this answer will be determined by the quality of communication as wellas the standard of the scientific response.

0 marksNo relevant content

Level 1 (1–2 marks)There is a basic method, which includes some of the apparatus,and there is someattempt at explaining some of the steps. The method does not necessarily allow theprocedure to be completed successfully by another person.There may be an attemptat identifying safety precautions but these may be inappropriate or incomplete.

20

Level 2 (3–4 marks)There is a clear description of the method, which includes most of the apparatusneeded, and an explanation of the various steps in the procedure. The method couldbe followed by another person. There is some attempt at identifying some, but notnecessarily all, of the safety precautions needed.

Level 3 (5–6 marks)There is a clear, balanced and detailed description of the method, which correctlynames the apparatus needed and explains the purpose of each step.This methodcould easily be followed by another person. There is a comprehensive list ofappropriate safety precautions.


examples of chemistry points made in the response

extra information

• heat the sulfuric acid in a beaker and add the copper oxide with stirring

the underlined words are needed to gain each point

• because heating and stirring speed up the reaction

• until the copper oxide is in excess

• which means that the reaction has gone to completion

• f ilter the mixtureorpour the mixture through a funnel and filter paperorleave the mixture to stand and decant / pour off the excess liquid

• to remove the excess / unreacted copper oxide

• put the solution in an evaporating basin

• heat it gently so that (some of) the water evaporates

• when a saturated solution is formed or when crystals start to form, stop heating

• leave the solution to cool so that crystallisation can occur.

examples of the safety points made in the response

• wear safety goggles – to protect eyes because sulfuric acid is corrosive / anirritant / harmful

• care when heating – to protect against burns

• wash hands after the preparation – copper sulfate is harmful / a sensitiser

• care when handling glass apparatus – to protect against cuts

• do not add copper oxide to boiling acid as it may boil over6

(b) (i) anhydrous copper sulfate

do not accept ‘dehydrated’1

(ii) it (turns) blue1


because (dilute sulfuric acid) contains water or because (dilute sulfuric acid)rehydrates the crystals or because hydrated copper sulfate is formed

owtte

ignore references to forming a solution / dissolving1

[9]

(a) start line drawn in ink121

so it will run / dissolve in the solvent / split up

allow mixes with the spots1

spots under solvent or solvent above spots / start line1

so they will mix with solvent or wash off paper or colour the solvent or dissolve in thesolvent

1

(b) (i) contains A and E1

and one other (unknown substance)

if no other marks awarded, an answer saying it is made up of threecolours gains 1 mark

1

(ii) 45 or 46

allow any value from 45 to 461

18

allow any value from 16 to 20

award 1 mark if numbers correct but in cm1

(iii) 0.40

allow ecf from (b)(ii)

ignore units1

(c) fast red

allow ecf from (b)(iii)1

has same Rf value

allow none of them, as none has the same Rf value for 2 marks1


(d) any one from:

• more accurate• more sensitive• uses small quantities of samples• quicker / faster / more rapid• can link to mass spectrometer (MS)

1

[12]

(a) neutralisation

ignore reference to exothermic or endothermic1

22

(b) 2 HCl + CaO ➔ CaCl2 + H2O

accept multiples and fractions

formulae

ignore state symbols1

balancing (dependent on first mark)1

(c) (the carbonate has) fizzing / bubbles / effervescence

ignore dissolving

ignore gas produced1

(d) add excess calcium carbonate to acid (and stir) / add CaCO3 until fizzing stops

ignore heating the acid

accept answer using calcium oxide in place of calcium carbonate1

(remove excess calcium carbonate by) filter(ing)1

warm until a saturated solution forms / point of crystallisation / crystals start to form

do not accept heat until all water gone1

leave to cool

dependent on previous mark

If solution not heated allow leave to evaporate (1)

until crystals form (1)1

(e) (i) white precipitate / solid (forms)1

insoluble in excess or remains or no (further) change in excess

dependent on a precipitate / solid forming1


(ii) same result with magnesium (ions)

do not accept reference to any other ion(s) that do not give a whiteprecipitate

accept other named ions that do give a white precipitate1

(iii) flame test or description of flame test1

gives a red flame

accept brick red or orange-red or scarlet

do not accept crimson1

[13]

(a) any two from:

• temperature (of the HCl)• mass or length of the magnesium• surface area of the magnesium• volume of HCl

2

23

(b) (i) (a greater concentration has) more particles per unit volume

allow particles are closer together1

therefore more collisions per unit time or more frequent collisions.1

(ii) particles move faster

allow particles have more (kinetic) energy1

therefore more collisions per unit time or more frequent collisions1

collisions more energetic (therefore more collisions have energy greater thanthe activation energy) or more productive collisions

1

(c) (i) add (a few drops) of indicator to the acid in the conical flask

allow any named indicator1

add NaOH (from the burette) until the indicator changes colour or add theNaOH dropwise

candidate does not have to state a colour change but penalise anincorrect colour change.

1

repeat the titration1


calculate the average volume of NaOH or repeat until concordant results areobtained

1

(ii) moles of NaOH

0.10 × 0.0272 = 0.00272 moles

correct answer with or without working gains 3 marks1

Concentration of HCl

0.00272 / 0.005 = 0.544

allow ecf from mp1 to mp21

correct number of significant figures1

[14]

(a) 31124

(b) (i) any two from:• incorrect reading of thermometer / temperature• incorrect measurement of volume of acid• incorrect measurement of volume of alkali (burette).

2

(ii) glass is a (heat) conductor or polystyrene is a (heat) insulator

answer needs to convey idea that heat lost using glass or not lostusing polystyrene

accept answers based on greater thermal capacity of glass (suchas “glass absorbs more heat than polystyrene”)

1

(c) (i) temperature increases1

(ii) no reaction takes place or all acid used up or potassium hydroxide in excess1

cool / colder potassium hydroxide absorbs energy or lowers temperature

ignore idea of heat energy being lost to surroundings1

(iii) take more readings

ignore just “repeat”1

around the turning point or between 20 cm3 and 32 cm3

accept smaller ranges as long as no lower than 20 cm3 and nohigher than 32 cm3

1


(d) 1.61 or 1.6(12903)

correct answer with or without working scores 3

if answer incorrect, allow a maximum of two from:

moles nitric acid = (2 × 25 / 1000) = 0.05 for 1 mark

moles KOH = (moles nitric acid) = 0.05 for 1 mark

concentration KOH = 0.05 / 0.031

answer must be correctly rounded (1.62 is incorrect)3

(e) same amount of energy given out1

which is used to heat a smaller total volume or mixture has lower thermal capacityornumber of moles reacting is the samebut the total volume / thermal capacity is less

if no other marks awarded award 1 mark for idea of reacting faster1

[14]

(a) base line drawn in ink

explanation must match problem1

25

which will run (and confuse the spots)

or

spots under water will dissolve into water / wash off1

(b) (i) copper(II) and iron (III)1

(ii) orange / brown

accept rusty1

(iii) Fe(OH)3

accept formula of complex [Fe(H2O)3(OH)3] or any other formula forhydrated iron oxide,such as Fe2O3.9H2O

1

(c) (i) distance moved by spot X: 2.1,

both needed for mark

distance moved by solvent from baseline: 5.0

allow ± 0.1 cm

accept answers in mm (21 and 50 ± 1 mm) and units stated as mm1


cm

correct unit used at least once1

(ii) 2.1 / 5.0

allow ecf from table

= 0.42

ignore units given in answer for Rf

1

(d) (i) substances B and D

both required1

(ii) do chromatography on mixture using ethanol or propanone as the solvent

accept conducting chromatography using any other solvent, butsuch answers cannot score second mark

1

result gives different Rf values

ie if ethanol solvent, B gives 0.62, D gives 0.45; if propanone, B gives 0.84,D gives 0.31

or

do chromatography on pure samples of B, D and mixture in ethanol orpropanone (1)

allow water under same conditions as solvent

position of unknown spot will match that of either pure B or pure D inchromatogram (1)

1

[11]


name: chemistry paper 1 required - a. hammond...

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